The acidity or alkalinity of an unknown aqueous solution is indicated by its
(1) ph value
(2) electronegativity value
(3) percent by mass concentration
(4) percent by volume concentration

The correct answer is Option 1.

Explanation:

pH is defined as power of hydrogen ions. It is the negative logarithm of hydrogen ion concentration. It ranges from the scale of 0 to 14. It helps to determine the acidity or alkalinity of the solution.

Mathematically,

When pH of the solution ranges from 0 to 6.9, it is said to be acidic and when it ranges from 7.1 to 14, it is said to be basic solution. And if the pH of the solution is 7, the solution is said to be Option 1.

Hence, the correct answer is Option 1.